I posted this also to ask.clojure.org forum at https://ask.clojure.org/index.php/8450/strange-behavior-with-clojure-java-io-copy
On Sunday, August 25, 2019 at 8:05:57 PM UTC+3, Juha Syrjälä wrote: > > Hi, > > I found a strange behavior in implementation of clojure.java.io/copy > function > > > https://github.com/clojure/clojure/blob/ee1b606ad066ac8df2efd4a6b8d0d365c206f5bf/src/clj/clojure/java/io.clj#L391 > (defn copy > "Copies input to output. Returns nil or throws IOException. > Input may be an InputStream, Reader, File, byte[], char[], or String. > Output may be an OutputStream, Writer, or File. > Options are key/value pairs and may be one of > :buffer-size buffer size to use, default is 1024. > :encoding encoding to use if converting between > byte and char streams. > Does not close any streams except those it opens itself > (on a File)." > {:added "1.2"} > [input output & opts] > (do-copy input output (when opts (apply hash-map opts)))) > > Actual copying is implemented here when copying from an InputStream to an > OutputStream. > > > https://github.com/clojure/clojure/blob/ee1b606ad066ac8df2efd4a6b8d0d365c206f5bf/src/clj/clojure/java/io.clj#L306 > (defmethod do-copy [InputStream OutputStream] [^InputStream input > ^OutputStream output opts] > (let [buffer (make-array Byte/TYPE (buffer-size opts))] > (loop [] > (let [size (.read input buffer)] ;;; XXX point 1 > (when (pos? size) ;;; XXX point 2 > (do (.write output buffer 0 size) > (recur))))))) > > Here .read function at point 1 is > https://docs.oracle.com/javase/7/docs/api/java/io/InputStream.html#read(byte[]) > > The javadoc states following > > Reads some number of bytes from the input stream and stores them into the > buffer array b. The number of bytes actually read is returned as an > integer. This method blocks until input data is available, end of file is > detected, or an exception is thrown. > > If the length of b is zero, then no bytes are read and 0 is returned; > otherwise, there is an attempt to read at least one byte. If no byte is > available because the stream is at the end of the file, the value -1 is > returned; otherwise, at least one byte is read and stored into b. > > --- > > > Meaning that return value -1 means end of stream, and return value 0 > doesn't mean end of stream. However condition at point 2 in code above, > stops recursion when .read returns value that is smaller than 1. > > > Now consider a case where .read returns this sequence of values in > consecutive calls: > > > 1024, 0, 1024, 201, -1 > > > clojure.java/io copies only the first 1024 bytes, when the whole stream > has 2249 bytes. Is this the intended behavior? Should the condition at > point 1 be "(not (neg? size))" ? > > > > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/039a4a5d-75d3-4da9-8da1-d3af340989cc%40googlegroups.com.
